1. Field of the Invention
The present invention relates to a modified aluminum oxy compound, a polymerization catalyst containing said modified aluminum oxy compound as a component, and a process for producing a polymer with said catalyst.
2. Description of the Related Arts
Many processes for producing an olefin polymer with a polymerization catalyst using a transition metal compound (for example, a metallocene and non-metallocene compound) and an aluminum oxy compound, are well-known. For example, a process using bis(cyclopentadienyl)zirconium dichloride and methylaluminoxane, is reported in JP58/019309A. However, in order to obtain the olefin polymer at a high yield, it is necessary to add a large amount of the aluminum oxy compound such as 1000 to 10000 moles of aluminum atom per 1 mole of transition metal atom. This has lead to major problems such as a high production cost and the residue of a large amount of aluminum atoms in the olefin polymer causes a bad influence on the properties of the olefin polymer.
In order to solve these problems, many reports concerning the reduction of the amount of aluminum oxy compound used have been made. For example, processes using a transition metal compound and a combination of an aluminum oxy compound and an organoaluminum compound are reported in JP60260602A and JP60130604A. Further, a process using methylaluminoxane and an aluminum oxy compound in which at least one isobutyl group is bonded with an aluminum atom, and a metallocene complex, and the like, are reported in JP63130601A. However, these processes do not reach a sufficient solution of the above-mentioned problems.
Further, polymers obtained with these catalysts have a low molecular weight in general, and the improvement has been further required for practical use.
A process using an aluminum oxy compound having an electron withdrawing group or an electron withdrawing group-containing group as an olefin polymerization catalyst component is recently reported in JP06329714A. According to this process, a highly active catalyst can be obtained, and an olefin polymer with a relatively high molecular weight can be obtained by polymerizing an olefin using said catalyst. However, the catalyst activity and the molecular weight of the olefin polymer obtained are not always sufficient, the invention of an aluminum oxy compound for realizing the more improvement of activity and the molecular weight of a polymer has been desired in order to produce an industrially useful olefin polymer.
Moreover, various investigations for synthesis of an α-olefin polymer having stereoregularity using a metallocene complex have been further carried out, and a trial of synthesizing a highly stereoregular α-olefin polymer by designing the structure of a metallocene complex is carried out.
For example, a production example of a highly stereoregular isotactic propylene polymer using a metallocene complex in which a methyl group is introduced at 2-position of the indenyl group of a silicon-bridging type bis(indenyl)complex and an isopropyl group, a phenyl group or a naphthyl group is introduced at 4-position (Organometallics 1994, 13, 954.), and a production example of a highly stereoregular isotactic propylene polymer using a metallocene complex in which two of mono- to tri-substituted η5-cyclopentadienyl groups are bridged (JP-B-258725, JP-B-2627669 and JP-B-2668732) are known.
Further, it is reported that a syndiotactic propylene polymer is obtained by using an aluminum oxy compound with isopropylidene(cyclopentadienyl)(fluorenyl)zirconium dichloride which is a metallocene complex having Cs symmetry, or the like (J. Am. Chem. Soc., 1988, 110, 6255.).